The present invention relates to an Integrated Circuits (ICs) package and assembly thereof, and more particularly to an integrated circuits (ICs) package and assembly thereof utilizing chip-on-glass (COG) assembly without anisotropic conductive film (ACF).
Generally, a flat panel display, such as a liquid crystal displays (LCDs) or a plasma display panels (PDPs), utilizes a semiconductor element such as an IC chip to control image display thereon. Chip-on-glass (COG) structure is widely used in IC assembly, in which the driving IC chip is assembled directly on the insulating substrate of the flat panel display.
FIG. 1A and FIG. 1B show a conventional COG structure. As shown in FIG. 1A, a plurality of bumps 210 is disposed on the IC chip 20, and a plurality of electrode pads 110 corresponding to the bumps 210 is disposed on the insulating substrate 10. In assembly, a layer of ACF 30 which comprises conductive particles 310 is coated on the insulating substrate 10, and the IC chip 20 is pressed on the insulating substrate 10 as shown in FIG. 1B. The IC assembly is then placed under predetermined environmental pressure and temperature for a certain period of time so that the insulating substrate 10 and the IC chip 20 are adhered together by the ACF 30. Further, the bumps 210 on the IC chip 20 and the electrode pads 110 on the insulating substrate 10 are electrically connected respectively by the conductive particles 310 in the ACF 30. Generally, the bumps 210 are formed substantially identical size and height, and the pressing surfaces of the bumps 210 are formed as a flat surface to ensure the electrical connection between the bumps 210 and the electrode pads 110.
However, the conductive particles 310 may not be uniformly distributed in the ACF 30. It is possible that density of the conductive particles 310 in a certain area of the ACF 30 is relatively lower or higher. In either case, electrical connection in the IC assembly may be deteriorated.
FIG. 1C shows an example in which density of the conductive particles 310 in a certain area of the ACF 30 is relatively lower. In FIG. 1C, the area A between the bump 210 and the electrode pad 110 does not contain any conductive particles 310. Thus, a large resistance exists in the area A, and the bump 210 and the electrode pad 110 fail in the electrical connection.
On the other hand, FIG. 1D shows an example in which density of the conductive particles 310 in a certain area of the ACF 30 is relatively higher. In FIG. 1D, a large number of the conductive particles 310 accumulate in the area B between adjacent bumps 210, which leads to shorting in the area B.
Further, the ACF 30 is expensive due to addition of the conductive particles 310, the distance between the adjacent bumps 210 or the adjacent electrode pads 110 is limited by the size of the conductive particles 310 (for example, a diameter of 5 micrometers), and the density of the conductive lines is also limited. Additionally, the problem of the density of the conductive particles mentioned above brings large resistance and electrical connection failure by the reasons other than that shown in FIGS. 1C and 1D.